1177 / 2024-09-20 15:52:38

Enhanced aerosol-iron dissolution and its environmental impacts in the East Asian outflow regions during long-range transport of Asian dust

aerosol-iron dissolution,aging processes,environmental impacts,East Asian outflow regions,Asian dust

Session 10 - The biogeochemistry of trace metals in a changing ocean

Iron (Fe), as a limiting and essential element for life, plays a pivotal role in biogeochemical cycles and has therefore become a focus of international research. In this study, we established a regional dust observation network in eastern China (Beijing, Handan, Yantai, Qingdao, Nanjing, and Hangzhou) during two Asian dust events in spring 2023, to elucidate the processes of aerosol Fe dissolution and assess its environmental impacts on the Northwest Pacific Ocean (NWPO). Our findings revealed that two dust events were transported from north to south through the North China Plain and the Shandong Peninsula, continuing over the Yellow Sea and East China Sea, and finally reached the Yangtze River Delta region. Simultaneously, the dust drifted from west to east to the NWPO. During the transport, Fe dissolution across eastern China in particles exhibited a significant spatial pattern, with iron solubility being "low in the north and high in the south". Specifically, Fe solubility in south China increased by 167% to 436% compared to that in north China. With the long-range transport of dust, the proportion of secondary inorganic aerosols (SIA) increased, and the aerosol aging processes played a significant role in enhancing Fe dissolution. It was also found that acidification driven by inorganic and organic acids has a synergistic effect to promote iron dissolution. Organics (oxalic acid), in particular, intensified aerosol acidification during two dust events, substantially boosting Fe solubility. The long-range transport of dust also had a profound impact on the marine environment, contributing to a significant increase in chlorophyll-a concentrations at the surface of the NWPO. Chlorophyll-a levels rose by an average of 80% during two dust events, compared to the historical period (2011-2020). Using the ratio of chlorophyll to carbon biomass (chl: C), we estimated the marine net primary productivity (NPP) to be approximately 0.8 mgC m⁻² d⁻¹. This study underscores the critical role of aerosol acidification in Fe dissolution during Asian dust outflows and highlights its subsequent environmental impacts on marine ecosystems. These findings contribute to a deeper understanding of the interactions between terrestrial pollutant transport, human activities, and nutrient deposition, shedding light on their implications for iron global biogeochemical cycles.